Yet on the eve of the debate, polls showed a close race. How … could someone like Mr. Trump have been in striking position for the White House? (He may still be there, since we have yet to see what effect the debate had on the polls.)

Part of the answer is that a lot more Americans than we’d like to imagine are white nationalists… Indeed, implicit appeals to racial hostility have long been at the core of Republican strategy…

But while racially motivated voters are a bigger minority than we’d like to think, they are a minority. And as recently as August Mrs. Clinton held a commanding lead. Then her polls went into a swoon.

What happened? … As I’ve written before, she got Gored. That is, like Al Gore in 2000, she ran into a buzz saw of adversarial reporting from the mainstream media, which treated relatively minor missteps as major scandals, and invented additional scandals out of thin air.

Meanwhile, her opponent’s genuine scandals and various grotesqueries were downplayed or whitewashed…

I still don’t fully understand this hostility, which wasn’t ideological. Instead, it had the feel of the cool kids in high school jeering at the class nerd. Sexism was surely involved but may not have been central, since the same thing happened to Mr. Gore.

In any case, those of us who remember the 2000 campaign expected the worst would follow the first debate: Surely much of the media would declare Mr. Trump the winner even if he lied repeatedly. …

Then came the debate itself, which was almost unspinnable. Some people tried…

But … tens of millions of Americans saw the candidates in action, directly, without a media filter. For many, the revelation wasn’t Mr. Trump’s performance, but Mrs. Clinton’s: The woman they saw bore little resemblance to the cold, joyless drone they’d been told to expect.

How much will it matter? My guess — but I could very well be completely wrong — is that it will matter a lot. …

But things should never have gotten to this point, where so much depended on defying media expectations over the course of an hour and a half. And those who helped bring us here should engage in some serious soul-searching.